Clinical and molecular characteristics associated with high PD-L1 expression in EGFR-mutated lung adenocarcinoma

Objective: Recent evidence suggests that elevated levels of PD-L1 expression may be linked to early resistance to TKI and reduced survival in NSCLC with EGFR mutations. This study aimed to characterize the clinical and molecular features of EGFR-mutated lung adenocarcinomas and determine the prognostic significance associated with high PD-L1 expression. Materials and methods: We conducted a retrospective chart review of 103 consecutive patients with advanced EGFR-mutated NSCLC, who received treatment between 01/01/2016 and 30/12/2020, at our institution. Results: Among the tumors, 17% (n = 18) exhibited high PD-L1 expression (≥50% tumor proportion score), which was associated with a lower prevalence of common EGFR mutations (56% vs. 82%, p = 0.03) and a higher frequency of complex EGFR mutations (28% vs. 7%, p = 0.02). Univariate analysis did not reveal any significant differences in first-line response, progression-free survival, or overall survival between the PD-L1 ≥50% and 50% group (7% vs. 17%, p = 0.19). Conclusion: High PD-L1 expression was more commonly found in lung adenocarcinomas with uncommon and complex EGFR mutations. Furthermore, high PD-L1 expression independently predicted poor survival. These findings warrant validation through prospective studies.